This application is based upon and claims the benefit of priority of Japanese Patent Applications No. H.11-196347 filed on Jul. 9, 1999, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a vehicle brake apparatus for controlling brake pressure with rotary pumps such as trochoid pumps.
2. Description of Related Art
In a conventional vehicle brake apparatus having a anti-skid control (hereinafter called ABS) actuator, plunger type pumps have been utilized as pumps for the ABS actuator. However, according to a recent demand of a more compact ABS actuator whose volume efficiency is higher, rotary pumps such as trochoid pumps, have become promising in place of the plunger type pumps having a limit for further improvement.
In each of the rotary pumps such as the trochoid pumps, the pump is formed in a near round shape, inlet and outlet of the pump are generally positioned symmetrically and fluid passages constituting intake and discharge ports of the pump extending from the inlet and outlet are also arranged symmetrically with respect to a diameter direction of the near round shape.
However, the rotary pump having such a construction has a problem that, when air is invaded into the inside of the pump, the air can not be easily purged since the intake and discharge ports or at least the discharge port does not extend in a direction opposite to a gravity direction.
An object of the present invention is to provide a vehicle brake apparatus with a plurality of rotary pumps each having a construction that air may be easily purged from the inside of the pump in a direction opposite to a gravity direction.
To achieve the object, a drive shaft for driving the plurality of the rotary pumps extends perpendicularly to the gravity direction and respective discharge ports of the rotary pumps extend in a direction opposite to the gravity direction.
It is preferable that brake fluid passages of the housing, where the plurality of the rotary pumps are housed and each of which is connected to each of the intake and discharge ports, extend in an opposite direction to the gravity direction.
To form the discharge port of each of the rotary pump as mentioned above, each of a pair of side plates is provided, at an end surface thereof on a side of a rotating portion (inner and outer rotors), with a ring shaped first groove formed so as to surround the drive shaft. Sealing members are disposed in the first grooves of the side plates so that the inner and outer rotors of each of the rotary pumps may be put between the pair of the sealing members and a groove space may be formed between the first groove and the sealing member in each of the side plates. Brake fluid flows along a longitudinal direction of the groove space.
With this construction, at least one of the pair of side plates is further provided with a discharge fluid passage extending in an opposite direction to the gravity direction from the highest position of the groove space. The groove space and the discharge fluid passage may constitute the discharge port.
Further, each sealing member is arranged to come in contact with an inner circumference of the first groove but at least partly in no contact with an outer circumference of the first groove so that the groove space may be formed outside an outer circumference of the sealing member and within the outer circumference of the first groove.
Preferably, the side plates, that are arranged between adjacent two of the rotary pumps, come in contact with each other so as to be divided in a direction nearly perpendicular to an axis of the drive shaft. As the side plates between the adjacent two pumps are divided into two, adequate positioning of the parts and components of respective pumps are easily secured independently of each other.
A housing has a recess whose center axis is nearly perpendicular to the gravity direction. The pump is inserted into the recess in such a manner that the drive shaft is positioned in parallel with the center axis of the recess.
It is preferable to provide a first spring member, which is disposed between a bottom of the recess and a leading end of the pump in an inserting direction thereof into the recess, for urging the pump in a direction opposite to the inserting direction thereof into the recess. By urging the pump as mentioned above, the rotary pumps are rigidly held in the housing so that the drive shaft may be stably and smoothly rotated.
In addition to or in place of the first spring member, a second spring member may be disposed at an entrance of the recess for urging the pump in an inserting direction thereof into the recess. This also serves to rotate the drive shaft stably and smoothly.
Further, a screw member is, preferably, disposed at the entrance of the cylindrical recess for urging the pump in the inserting direction thereof into the recess to hold more rigidly the pumps in the housing.
In a case that the pump and the recess are respectively formed in a cylindrical shape, an inner circumference surface of the cylindrical recess may be provided with ring shaped second grooves, each of which is formed so as to surround an outer circumference of the pump and to communicate with any one of the intake ports and the discharge ports. The housing is provided with brake fluid passages each connected to the highest position of each of the second grooves so that air entered into the second grooves may be moved toward the highest position thereof and purged into the brake fluid passages.
The brake apparatus is further provided with a holder having a holder through hole, a motor having a motor shaft which is coupled with the drive shaft, and a bearing fitted to an inner circumference surface of the holder through hole and an inner circumference surface of the side plate hole. The motor is fixed, via the holder, to a surface of the housing where the recess is provided perpendicularly thereto in such a manner that the motor shaft may be positioned in a center axis line of the holder through hole. The bearing slidably holds at least one of the motor shaft and the drive shaft. With the construction mentioned above, the bearing serves to align center axes of the motor shaft and the drive shaft.
Preferably, the drive shaft is provided, at a leading end thereof, with a stopper restricting an excessive axial movement thereof so that the drive shaft may not get out of the pump.
Further, the drive shaft is provided with a plurality of key holes, each of which is longer in an axial direction of the drive shaft, and a plurality of keys, each of which is housed in each of the key holes so as to slide relatively to the drive shaft in an axial direction thereof but to transfer torque for driving the inner rotors from the drive shaft to the respective inner rotors. With the construction of key holes and keys mentioned above, even if the drive shaft is moved in an axial direction thereof, the keys are not pressed by the drive shaft so that the torque may be transferred to the inner rotors.